Enhanced Activation Energy Released by Coordination of Bifunctional Lewis Base d-Tryptophan for Highly Efficient and Stable Perovskite Solar Cells

Perovskite defect passivation with molecule doping shows great potential in boosting the efficiency and stability of perovskite solar cells (PSCs). Herein, an efficient and low-cost bifunctional Lewis base additive d-tryptophan is introduced to control the crystallization and growth of perovskite grains and passivation defects. It is found that the additive doped in the solution precursors could retard crystal growth by increasing activation energy, resulting in improved crystallization of large grains with reduced grain boundaries, as well as inhibiting ion migration and PbI2 aggregation. As a result, the PSCs incorporated with d-tryptophan additives achieve an improved power conversion efficiency from 18.18 to 21.55%. Moreover, the d-tryptophan passivation agent improves the device stability, which retains 86.85% of its initial efficiency under ambient conditions at room temperature after 500 h. This work provides Lewis base small-molecule d-tryptophan for efficient defect passivation of the grain boundaries toward efficient and stable PSCs.